I've got a '7427 system that is running on a IH345 - I've got good fuel and timing adjustments. I've been through 3 PCMs (All '7427 $0D) now and I still can't figure out my high idle/oscillating problem.

The best I can tell I have a wandering IAC. From a cold start it works reasonably well. If you stop then start the engine and it will high idle. I'm assuming the cause is the IAC being too open and more fuel being called for to richen it. The TPS is around 0.55v (+/- .01v), but the TP Dash throttle reads about 10%. I've set the target idle speed to all engine temperatures to 650. So it should never reach over 700. But it'll idle 1100-1400! I have the manual flag set.

Without a P/N switch, how does someone adjust the throttle plate? I've never got the shorting of the pin trick to close the IAC to work.

This is creating a safety issue since I have an auto trans (727) I have to brake harder to overcome the added power to the torque converter.